We survey results of computer simulations for the structure and dynamics supercooled polymer melts films. Our is mainly concerned with features a coarse grained model—a bead–spring model—in temperature regime above critical glass Tc ideal mode-coupling theory (MCT). divide our discussion into two parts: part devoted to bulk properties dealing thin The focuses on aspects: comparison simulation MCT an analysis dynamic heterogeneities. explain in detail how analyses are performed what may be...

We present results of molecular-dynamics simulations for a nonentangled polymer melt confined between two completely smooth and repulsive walls, interacting with inner particles via the potential U(wall)=(sigma/z)(9), where z=/z(particle)-z(wall) sigma is (roughly) monomer diameter. The influence this confinement on dynamic behavior studied various film thicknesses (wall-to-wall separations) D, ranging from about 3 to 14 times bulk radius gyration. A comparison mean-square displacements in...

Using molecular dynamics simulations, we show that a simple model of glassy material exhibits the shear localization phenomenon observed in many complex fluids. At low rates, system separates into fluidized band and an unsheared part. The two bands are characterized by very different probed local intermediate scattering function. Furthermore, stick-slip motion is at small rates. Our results, which open possibility exploring rheological behavior using compared to recent experiments on various...

A coarse-grained bead spring model of short polymer chains is studied by constant pressure molecular dynamics (MD) simulations. Due to two competing length scales for the effective bonds and energetically preferred distance between nonbonded beads, one observes a glass transition when dense melts are cooled down (as shown in previous work, at p=1 mode coupling critical temperature Tc≈0.45 Vogel–Fulcher T0≈0.33, Lennard-Jones units). The present work extends these studies, estimating...

A tutorial introduction to the technique of molecular dynamics (MD) is given, and some characteristic examples applications are described. The purpose scope these simulations relation other simulation methods discussed, basic MD algorithms sampling intensive variables (temperature T, pressure p) in runs carried out microcanonical (NV E) ensemble (N = particle number, V volume, E energy) as well realization ensembles (e.g. NV T ensemble). For a typical application example, molten SiO2,...

Polymeric thin films of various thicknesses, confined between two repulsive walls, have been studied by molecular dynamics simulations. Using the anisotropy perpendicular, PN(z), and parallel components, PT(z), pressure tensor surface tension system is calculated for a wide range temperature film thicknesses. Three methods determining are compared: method Irving Kirkwood (IK), an approximation thereof (IK1), Harasima (H). The IK- H-methods differ in expression PT(z) (z denotes distance from...

The stress-strain relations and the yield behavior of model glass (a 80:20 binary Lennard-Jones mixture) is studied by means MD simulations. First, a thorough analysis static stress presented via simulations under imposed stress. Furthermore, using steady shear simulations, effect physical aging, rate temperature on relation investigated. In particular, we find that at point (the ``peak''-value curve) exhibits logarithmic dependence both ``age'' system in qualitative agreement with...

A thorough study of shear stress within the lattice Boltzmann method is provided. Via standard multiscale Chapman-Enskog expansion we investigate dependence error in on grid resolution showing that obtained by second-order accurate. This convergence, however, usually spoiled boundary conditions. It also investigated which value relaxation parameter minimizes error. Furthermore, for simulations using velocity conditions, an artificial mass increase often observed. a consequence...

Via computer simulations, we provide evidence that the shear rate induced red blood cell tumbling-to-tank-treading transition also occurs at quite high volume fractions, where collective effects are important. The takes place as ratio of effective suspension stress to characteristic membrane exceeds a certain value and does not explicitly depend on fraction or deformability. This coincides with for from an orientationally less ordered highly phase. average deformation show any signature...

Using nonequilibrium molecular dynamics simulations, we compute the shear viscosity, ηs, of a glass forming polymer melt at temperatures ranging from normal liquid state down to supercooled state. For this purpose, is confined between two solid walls and constant force pointing in direction parallel applied on each monomer thus giving rise Poiseuille flow. It shown that ηs(T) does not exhibit an Arrhenius-type behavior but can be described both by power law (mode coupling theory)...

We study the shearing rheology of dense suspensions elastic capsules, taking aggregation-free red blood cells as a physiologically relevant example. Particles are non-Brownian and interact only via hydrodynamics short-range repulsive forces. An analysis different stress mechanisms in suspension shows that viscosity is governed by shear elasticity whereas forces subdominant. Evidence for dynamic yield above critical volume fraction provided related to properties capsules. The found follow...

We investigate the wetting behavior of liquid droplets on rough hydrophobic substrates for case that are comparable size to surface asperities. Using a simple three-dimensional analytical free-energy model, we have shown in recent letter [M. Gross, F. Varnik, and D. Raabe, EPL 88, 26002 (2009)] that, addition well-known Cassie-Baxter Wenzel states, there exists further metastable state where droplet is immersed into texture finite depth, yet not touching bottom substrate. Due this new state,...

Deformation of single stranded DNA in translocation process before reaching the pore is investigated. By solving Laplace equation a suitable coordinate system and with appropriate boundary conditions, an approximate solution for electric field inside outside narrow obtained. With analysis based on "electrohydrodynamic equivalence" we determine possibility extension charged polymer due to presence gradient vicinity entrance. multi-scale hybrid simulation (LB-MD), it shown that effective...

Recent experiments provide evidence for density variations along shear bands in metallic glasses with a length scale of few hundred nanometers. Via molecular dynamics simulations generic binary glass model, here we show that this is strongly correlated composition, coordination number, viscosity, and heat generation. Individual events the band path mean distance nanometers, comparable to recent experimental findings on medium range order. The aforementioned result from these localized...

Tissue degradation plays a crucial role in vascular diseases such as atherosclerosis and aneurysms. Computational modeling of hemodynamics incorporating both arterial wall mechanics tissue has been challenging task. In this study, we propose novel finite element method-based approach to model the microscopic walls its interaction with blood flow. The is applied study combined effects pulsatile flow on deformation intra-aneurysm hemodynamics. Our computational analysis reveals that leads...

We propose a scheme for simulation of the solute-driven dendritic solidification which accounts flows liquid and motion growing dendrites. The is based on multiphase-field method calculating lattice Boltzmann to simulate fluid flows. Motion rotation solid grains possible.

Spatial correlations of microscopic fluctuations are investigated via real-space experiments and computer simulations colloidal glasses under steady shear. It is shown that while the distribution one-particle always isotropic regardless relative importance shear as compared to thermal fluctuations, their spatial show a marked sensitivity competition between shear-induced thermally activated relaxation. Correlations in dominated regime, but develop strong anisotropy dominates dynamics...

The coalescence of two resting liquid droplets in a saturated vapor phase is investigated by Lattice Boltzmann simulations and three dimensions. We find that, the viscous regime, bridge radius obeys t^{1/2}-scaling law time with characteristic scale given time. Our results differ significantly from predictions existing analytical theories as well experimental observations. While underlying reason for these deviations presently unknown, simple scaling argument that describes our well.

In a recent paper [Mandal et al., Phys. Rev. E 88, 022129 (2013)], the nature of spatial correlations plasticity in hard-sphere glasses was addressed both via computer simulations and experiments. It found that experimentally obtained obey power law, whereas from are better fitted by an exponential decay. We here provide direct evidence---via glass two dimensions (2D)---that this discrepancy is consequence finite system size 3D simulations. By extending study to 2D soft disk model at zero...

Large scale molecular dynamics simulations are performed to study the steady state yielding of a well established simple glass. In contrast supercooled state, where shear stress, $\sigma$, tends zero at vanishing rate, $\gammadot$, stress plateau forms in glass which extends over about two decades rate. This strongly suggests existence finite dynamic yield glass, $\sigma^+ (T) \equiv \sigma(T; \gammadot \to 0) >0$. Furthermore, temperature dependence $\sigma^+$ discontinuity transition...

Effects of wall roughness/topography on flows in strongly confined (micro-)channels are studied by means lattice Boltzmann simulations. Whereas roughness macroscopic channels is considered to be relevant only for high-Reynolds-number turbulent (where the flow even smooth walls), it shown this paper that, micro-channels, surface may modify qualitative features flow. In particular, a transition from laminar unsteady observed. It found that roughness-induced enhanced as channel width decreased....

We introduce thermal fluctuations in the lattice Boltzmann method for nonideal fluids. A fluctuation-dissipation theorem is derived within Langevin framework and applied to a specific model that approximates linearized fluctuating Navier-Stokes equations fluids based on square-gradient free-energy functionals. The obtained noise shown ensure equilibration of all degrees freedom simulation high accuracy. Furthermore, we demonstrate satisfactory results most practical applications...

It is shown numerically that the deviatoric stress tensor second-order accurate in bulk Bhatnagar-Gross-Krook lattice Boltzmann (LB) method. In an earlier work [T. Krüger, Phys. Rev. E 79, 46704 (2009)], we have already predicted convergence. However, numerical simulations using a duct flow were not fully line with this prediction. particular, convergence rate of was observed to depend on LB boundary condition. present paper, examine pure system, decaying Taylor-Green vortex flow. Our...